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Old 12-10-2005, 04:34 PM
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Additional 50hp from heads, or 200+lbs off the nose from a LW front suspension clip?

I'm stuck in a rut...I'm dealing with a no-sponser, strictly 'fun' racing budget, as a lot of you fella's, so I figured I'd ask some of your opinions...

With my combo, AFR comp. 227's should yield an additional 50hp and 15-20ft/lbs at peaks, w/o losing much of anything under the curve over the current heads. Switching from iron to aluminum will drop 25 or so lbs as well. This is a high rpm N/A 388.

The vehicle in question is a '94 C1500 stripped for track duties, currently weighing 2900 or so lbs with draglites. Being a truck with a heavy OEM suspension system, a strange aluminum front drag strut/LW brakes/front frame clip combo should wipe at least 200lbs off the front (already manual rack&pinion equipped). Of course, this is sprung, unsprung, and rotating mass, all from the nose. Weight transfer would play a big part here...

Both options will cost about the same. Yes, one is one heck of a time consuming project, but don't consider this in your opinion. Which of the two should net better results at the track? If you have the time, please explain your opinion. I'm no 'newb' in the racing dept., but I appreciate others' educated opinions and 'theories'.

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Old 12-10-2005, 06:43 PM
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First off... have you weighed this thing lately? With driver ready to run, I would expect that truck to weigh at least 3700 lbs. To get that truck down to 2900, you must have lexan windows, glass or carbon body, no dash ect....

I would go with the front clip idea. If this is a truck that you really want to keep, it is something that will definately pay off. Heads and engines come and go, but the chassis usually stays around for a long time.
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Old 12-10-2005, 07:59 PM
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Rules of thumb on weight vs horsepower

100 lbs of chassis weight = 10 HP.
10 lb or centrifical weight = 10 HP.
Figure the math for yourself.
Centrifical weight is the weight of stuff like the wheels, tires, drive shaft, Internals of the transmission, flywheel and clutch.
This is an old axiom from my dirt track racing days.
You want to consentrate on reducing centrifical weight, as well as unsprung weight, and there are alot of ways to do that last one.
If you have disc brakes on the front, take the calipers off and clean them up on the outside with an offset grinder. Grind off all the casting plug dealies, flash from the mold etc. This can get you up to 4 lbs off of each front corner. I realize that doesnt mean a lot in drag racing, but it sure does when you go around corners. Other things to consider, are little gizmos like the sound deadeners used on the bolts that tie the body to the frame. Inside fender wells can be taken out as well. Run the smallest lightest aluminum or composite radiator that you can get away with and still keep your engine cool.
The only limitation is keeping the vehicle safe, and not go overboard.
If you can substitute suspension parts with aluminum, that will take a lot of static weight out of the vehicle.
If you are running a standard transmission, go with an aluminum flywheel and get rid of about 20-30 lbs of centrifical weight. Super light weight rims are a definate plus in this area as well.
Cubic Dollars = Linier Horsepower. How quick do you want to be?
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Old 12-10-2005, 08:02 PM
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Jeff:

No mistakes on the weight. Before the stripping, it weighed just over 3700 with me in it (you know your trucks lol). It's now just a shell with a steering wheel, gauges, and a swiss-cheese'd .080 thick seat. The steering column is CM tubing, and the steering rack is a manual 'pinto' unit. Pin-on 13lb hood, Percy's glass, no sway bar, plastic fuel cell, dry cell batt., misc. body metal removed from cab int., no dash, HVAC, panels, carpet or padding...I've gone as far as I can w/o chassis/suspension work, or more fiber body parts (which don't currently exist).

You made a good point with the 'engines come and go'. I've never looked at it that way. However, I'm moreso after which will is more likely to yield better ET's. The less-effective will still be done, just at a later date.
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Old 12-10-2005, 08:08 PM
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Max Kieth: I appreciate your input in the weight dept, but I'm just looking for which of the two options above should yield better results. I have a pretty good handle on shedding weight. Any more grinding and swiss-cheesing and we'll cross the 'unsafe' realm...
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Old 12-10-2005, 08:12 PM
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Anything one can do to reduce weight is HP gained..Depends on what one wants to spend but I woudl go with a lighter chassis if possible and gut out everything that does not absolutely need to be there..And yeah engines do come and go..

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Old 12-10-2005, 08:24 PM
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Understood. Rule of thumb: 100lbs=.1; 10hp=.1...In this case, that would mean .5 (heads), or .2 (front clip) off the ET. Unfortunately though, with the 200lbs being a mix of sprung, unsprung, and rotational mass, things are a bit different. Not to mention, going from gooey OEM springs and shocks to pieces made for drag racing. Something tells me both would yield close results, but that's why I'm asking for outside opinions...I think the heads would make for more mph, and the front clip more of an ET drop. But again, I don't know...
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Old 12-10-2005, 10:09 PM
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Going on a diet

As was mentioned, any weight reduction is going to help. But remember that the more weight you take out that you cant transfer to plant the rear on take off, is going to make launching all that much more difficult.
For my money, I would consentrate on getting the weight out first, and safely. Then work to make the suspension work with the weight. Then work on the monster firebreathing butt whoopin engine. Engines tend to break and make expensive noises more readily than chassis parts.
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Old 12-11-2005, 12:37 AM
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The weight is already out lol. I'm out of options there, with the exception of the chassis and suspension, which is what brings me to this decision. The butt-kicking engine is already built. The only change would be the heads, a little manifold work, and some carb tweaking. Anything off the nose should help weight transfer and traction with good driver, especially being a front-heavy truck. That doesn't worry me.

An educated guess from some experienced fello gearheads would really make my day. Providing a consistant, experienced driver, which would most likely yield the largest ET drop:


A: An additional 50hp and 15-20ft/lbs.

B: Aluminum front drag struts, brakes, and CM front frame clip (loss of 200-250lbs of sprung, unsprung, and rotating mass).


Again, thanks.


EDIT: Kieth, I seem to have missinterpreted your last post a bit...I just reread it and see you were on-target. I'm really not worried about what lasts longest, though, to be honest with you. The struts will need rebuilding at some point, the rotors will wear, etc. just like the heads. I'm just gauging ET drop of the two. If I knew exact weights of things, an equasion could be setup, but, no such luck...

Last edited by NLang; 12-11-2005 at 12:48 AM.
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Old 12-11-2005, 10:16 AM
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Going on a diet

Something just occured to me, on your losing front end weight. You might consider going with a straight axle front end, with a split wishbone configuration for trailing arms, coil overs, and run a panard bar. With this setup you could get a lot of front end weight out of the vehicle. This would allow you to also take some weight out of the front crossmember as well. You could lose maybe another 50-100 lbs by getting rid of the double A arm front end. Another alternative would be to run the straight axle with composite or fiberglass leaf springs, doing away with both the wishbones and the panard bar.
Look at Speedway Motors stuff at speedwaymotors.com, and with some measuring, I think you would find the kind of straight axle setup that would fill your need. Also, you would want to run 4 inch wide rims with a very skinny 85 series tire on them. This would also, if you are into the looks of things, give you a really retro gasser look. HEHE.
Run 90/10 uplift shocks on the front. This will allow the front of the vehicle to come up easily and transfer a lot of weight to the rear, and keep the front end up for a much longer period, keeping the weight back on the rear, especialy during the Low and second gear traversements.
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Old 12-11-2005, 12:48 PM
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Max has a lot of excellent experience and conveys it well, thanks Max.
I always appreciate your input.

The only thing that I might question in this entire thread is the flywheel weight from the pure weight standpoint. A lighter flywheel should be an afterthought.. later..a tuning help.... Lighter flywheels often lessen the launch-tire-spin and allow the engine to rev quicker through the gears.. That seems to me to be a "try and see" thing.

I am not exactly sure how weight reduction equates to torque converters since most people are only concerned with stall speed... and some converters have gotten pretty small diameter.

I run a stick shift car...... Ancient technology....

Last edited by xntrik; 12-11-2005 at 12:55 PM.
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Old 12-11-2005, 01:51 PM
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Quote:
Originally Posted by xntrik
Max has a lot of excellent experience and conveys it well, thanks Max.
I always appreciate your input.

The only thing that I might question in this entire thread is the flywheel weight from the pure weight standpoint. A lighter flywheel should be an afterthought.. later..a tuning help.... Lighter flywheels often lessen the launch-tire-spin and allow the engine to rev quicker through the gears.. That seems to me to be a "try and see" thing.

I am not exactly sure how weight reduction equates to torque converters since most people are only concerned with stall speed... and some converters have gotten pretty small diameter.

I run a stick shift car...... Ancient technology....
The lighter flywheel/flexplate will negatively effect your 60' time and reaction time. Aheavier one will keep the RPMs more consistant on the launch, and not let the engine bog as bad.

When you lighten up a car, the stall speed of the converter will DECREASE. Since there is less resistance, it is easier for the car to move, which will cause less slippage in the converter- thus a lower stall speed.

For the truck- I would take a look at the strut front ends from ARC and Competition Engineering. That seems to be the lightest design, and that is what most of the chasis cars are being built with.
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Old 12-11-2005, 03:59 PM
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Flywheel weight and launch power

I do admit that is an interesting dicotomy. If you are running an automatic transmission, you are definately limited on flywheel weight, since going with an aluminum flex plate would be such a minute change as to not make any difference,andan aluminum flex plate would probably deteriorate much quicker as well, even to the point of not being able to handle the power given to it do to the need of the thinness of the material in a flexplate. However, an aluminum flywheel with a manual transmission will make a big difference in launch. While a heavier flywheel does store more energy, the initial surge when dropping the clutch would seem to vote in favor of the higher weight of the steel flywheel, but the ability of the engine to rev faster with the lighter aluminum unit seems to nullify the stored energy of the heavier steel flywheel. It is possible that sometimes the lighter flywheel could be a disadvantage. Ive never taken much stock in 60' times other than to compare my launch times for consistancy, and there are other things that can be done to reduce 60' times, like lots of practice on reaction time. That in itself can be the difference between winning and losing. I did watch some pros dragracing on TV the other night, and the winner actually came down to a .003 seconds difference in reaction time. The race is won at the other end of the track, and the faster revving with the lighter rotating mass will defniately win out on the big end. Even a small displacement, low HP engine can benefit from lighter rotating mass, and to my jaundiced eye, even more than a monster firebreathing engine. A 700 HP engine will over come the constant energy build up of a heavier flywheel a lot quicker than will a 350 HP engine.
I dont know of any pro racer running a stock 40 lb flywheel. As far as running automatic goes, one is very limited in weight reduction, as even a 10 inch torque converter will weigh very close to that of a 12 inch. The advantage of the smaller converter is that while it is nominally lighter, it allows for higher stall speeds, and its weight is also closer to the axis of the rotating assembly. A good example of this is to get on a table capable of turning. Pick up a couple 5 lb dumbells in your hands.Get on the table and hold the weights close to your chest. After someone gives you a bit of spin, extend your arms out, with the weights in your hands and you will slow down. bring the weights in closer to your chest and you will speed up again.
I dont remember the $50 words my science teacher used to call this, but the effect is dramatic. The only time a heavy flywheel is advantagious is when either running at a constant RPM, or to enable a small engine to begin moving a heavy mass at just above idle RPM. Those of us gray beards that remember the great and venerable Flathead Ford V-8, remember the neat trick of shaving the flywheel. The stock unit could weigh as much as 120 Lbs. and was shaped roughly like a salad bowl. Machining the flywheel flat and removing the lip was a great boon to improving performance with the Flathead, and I dont remember anyone ever having any trouble getting a Flathead powered car moving from a stoplight with a shaved flywheel. It is a week bit harder to get a vehicle to idle away from a stoplight with a light flywheel than it is with a heavy one, but the ability of the engine to accelerate at a quicker rate will soon overtake the stored energy of the heavier unit.
The concept that lighter rotating mass will decrease wheel spin may or may not hold true. I dont have a science degree to debate that one, but if all other things are equal, I would still put my money on the lighter assembly.
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Old 12-11-2005, 06:49 PM
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I raced a '00 Trans Am with a T-56 the past few yrs, and we played the aluminum vs iron flywheel inertia game. The aluminum took the cake each time, though 60ft times with the heavy steel unit were consistantly better. Once pwr levels reached a certain point, and traction became the new battle, the aluminum unit took the advantage at all points, including 60-ft. Just our experience...

I just received a reply to an inquiry I sent to Strange a week or so ago about weight. He didn't specify the weight of the assembly, but he told me to expect at least a 350lb drop with this particular application This was not including the manual rack option, as I was sure to add that I was already equipped. Talk about making a hard decision simple lol...I had also asked about how it would stack-up to a front solid-axle configuration. In a nutshell, no competition...He was probably considering metal leaf springs, though. I didn't realize glass springs existed myself.

For those that don't know what 'kit' I'm refering to, go to Comp Engineering's website, and look under struts. You'll see the kits and frame clip. This setup uses a single 4130 a-arm. The top of the strut mounts to an appendage on the frame (less unsprung weight, less moving parts, etc.). They even have an extra LW spindle mount kit for you extra dedicated fellas.

For the guy on the vehicle weight vs converter topic, you're correct. TCI had me go with one step up in the stall dept. because I was still shedding weight. They said it definitely effects stall speed. It works the same way as if you were to trade your super-torquey BB for a SB.

3 cheers for all that gave their input. I really appreciate your time.
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Old 12-11-2005, 07:35 PM
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Max,
I definately agree with you on much of what you said. The decision of which way to go with the weight depends on the application. With most of today's race engines, 700 hp is extremely common. Almost all of the stockers and superstockers out there are using my flexplate, and they all use the lightweight version. They need the light weight since they are not as worried about consistancy as E.T. However, most of the big time bracket racers go with the heavier flexplate setup for the launch consistancy. This is also why you see "inertia rings" on the backside of most good race converters. This used to be a special "add on" feature, however they are commonplace now. When it comes to the weight of the torque converter, there is a HUGE difference in weight. Converters are part of my business, so I am pertty close when it comes to these weights. A 12" converter can weigh about 42-45 lbs (for a regular non-lockup trans), while a 10" is in the 32-35 range. The 8" and 9" converters actually weigh about the same as a 10" due to the extra strengthening that is built into them.

Sorry to get so off topic... maybe I should have started a new one.

NLang,
I think that you have your answer... the strut front end is something that you will not regret! If you need to adjust your converter or get a different one after you make this change, just let me know.
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